fix that alias can only exist once and when dublicate give error

browser_cli/cli.py

@@ -21,7 +21,13 @@ from browser_cli.commands.dom import dom_group
 from browser_cli.commands.extract import extract_group
 from browser_cli.commands.session import session_group
 from browser_cli.commands.search import search_group
-from browser_cli.client import send_command, BrowserNotConnected, REGISTRY_PATH, display_browser_name
+from browser_cli.client import (
+    send_command,
+    BrowserNotConnected,
+    REGISTRY_PATH,
+    active_browser_targets,
+    display_browser_name,
+)
 
 console = Console()
 
@@ -51,6 +57,30 @@ NATIVE_HOST_DIRS = {
 }
 
 
+def _rename_target_profile(target_browser: str | None) -> str | None:
+    if target_browser:
+        return target_browser
+
+    active = active_browser_targets()
+    if len(active) == 1:
+        return active[0].profile
+    return None
+
+
+def _ensure_unique_browser_alias(alias: str, target_browser: str | None) -> None:
+    target_profile = _rename_target_profile(target_browser)
+
+    profiles: dict[str, str] = {}
+    if REGISTRY_PATH.exists():
+        try:
+            profiles = json.loads(REGISTRY_PATH.read_text())
+        except Exception:
+            profiles = {}
+
+    if alias in profiles and alias != target_profile:
+        raise click.ClickException(f"Browser alias '{alias}' already exists")
+
+
 def _native_host_wrapper_path() -> Path:
     if sys.platform == "darwin":
         base_dir = Path.home() / "Library" / "Application Support" / "browser-cli"
@@ -184,6 +214,7 @@ main.add_command(clients_group)
 def cmd_clients_rename(target_browser, alias):
     """Set the profile alias used to identify this browser instance."""
     try:
+        _ensure_unique_browser_alias(alias, target_browser)
         send_command("clients.rename_profile", {"alias": alias}, profile=target_browser)
     except BrowserNotConnected as e:
         console.print(f"[red]Error:[/red] {e}")